1. Field of the Invention
The present invention relates to a document original simulator for image fogging detection for use in an image forming apparatus such as a copying machine, and an image fogging troubleshooting method and an image forming apparatus using such a document original simulator.
2. Description of Related Art
Copying machines are generally adapted to form an electrostatic latent image on a photoreceptor drum by exposing an original image to light, then develop the electrostatic latent image by means of a developing device for formation of a visible toner image on the photoreceptor drum, and transfer the toner image onto a recording sheet by means of a transfer device.
The assignee of the present invention has been making efforts to develop a self-recovery system which is adapted to detect, by means of a density detector, an imaging failure which may be caused by changes in conditions of a copying machine due to malfunction or aging of the copying machine, and to restore the copying machine to a normal state to allow for normal image formation.
More specifically, such a self-recovery system employs, for example, a document original simulator which has black, white and gray simulation portions. Densities of toner image portions corresponding to these simulation portions are preliminarily determined in a normal state by the density detector, and stored. In maintenance of the copying machine or after repair of the copying machine, densities of toner image portions corresponding to the black, white and gray simulation portions of the document original simulator are determined by the density detector.
If the densities thus determined are different from the densities determined in the normal state, density-related parameters such as the amount of light exposure, the charge potential of the photoreceptor and a developing bias are adjusted so that the densities of the toner image portions corresponding to the black, white and gray simulation portions of the document original simulator are equated with the corresponding normal toner image densities.